Delay-dependent stability and stabilisation of continuous 2D delayed systems with saturating control

This paper deals with the stabilisation problem of continuous two-dimensional (2D) delayed systems, in the presence of saturations on the control signals. For this, a new delay decomposition approach is proposed to deal with the stability and stabilisation issues. The idea is that the range of variation of each delay is divided into segments, and a specific Lyapunov– Krasovskii functional is used that contains different weight matrices in each segment. Then, based on this approach, new delay-dependent stability and stabilisation criteria for continuous 2D delayed systems are derived. These criteria are less conservative and include some existing results as special cases. Some numerical examples are provided to show that a significant improvement is achieved using the proposed approach.     

3D finite element modeling of 3D C2W (chip to wafer) drop test reliability: Optimization of internal architecture and materials

3D-WLSiP appears as a way to keep increasing density of microelectronic components. The C2W 3D integration use wafer-level processes to improve throughput. This technology gives a high yield and a good flexibility for the choice of internal architectures and assembling techniques. The reliability of 3D components has to be evaluated on mechanical demonstrator with daisy chain before real production. Modeling has proven to be a very efficient tool for design optimization. In this paper, 3D FEM modeling and submodeling techniques are employed to compare the dynamic response of several 3D C2W components under drop test loading conditions. The impacts of possible errors in thin layers elastic modulus estimation are studied. The behavior of the Face To Face (F2F) and the Back To Face (B2F) design for 3D integration are compared. The effects of TSVs repartition in silicon die and molding resin’s mechanical properties are discussed. The reliability evaluation criterion is chosen as maximum shear plastic strain of critical bump. The results have been used in choosing of the optimal design and materials properties for real production.     

High Performance Materials from Oriented Plastics

Molecular orientation of polymer chains affects considerably the final properties of plastic products, such as stiffness, creep and impact resistance, barrier properties and transparency. Different orientation processes, such as solid state extrusion, die-drawing and roll-drawing are currently being investigated in order to produce parts with large dimensions. Examples include the die-drawing process for the obtention of oriented tubes and shapes, roll-drawing for flat and simple geometry profiles as well as uniaxial and biaxial solid state extrusion. These processes have been used successfully to form different materials, from polyolefins to engineering and specialty resins, and mechanical properties comparable to fiber reinforced plastics have been achieved. Solid state forming was performed in our laboratories on several polymeric materials using rolling, roll-drawing and solid state extrusion. Significant improvements in the mechanical behavior were observed and materials with tensile modulus and strength above 10 GPa and 400 MPa, respectively, were obtained. An improvement in the transverse mechanical properties was also observed for the roll-drawn polymers.     

Polyethylene terephthalate/calcined kaolin composites: Effect of uniaxial stretching on the properties

This article is aimed at investigating the effect of a calcined kaolin filler (CKao) on polyethylene terephthalate (PET). The influence of a silane coupling agent, chain extension, and post extrusion uniaxial hot‐stretching on the final properties of the produced composites were studied as well. PET‐CKao films were prepared via melt blending using a twin‐screw extruder followed by stretching above the glass transition temperature at controlled conditions. The morphology of the composites before and after stretching was observed by SEM. Rheological measurements were also performed to characterize the polymer melts. Mechanical and optical properties as well as the oxygen transmission rate of the composites were also investigated. The results showed that addition of CKao particles, even at low filler content, improved drastically the mechanical and barrier properties compared to the neat PET. This effect was more pronounced in case of hot‐stretched samples. The main drawback observed with these CKao particle composites was an increased haze. Processing parameters including stretching temperature and stretching ratio were found to have a significant effect on the final properties; however, the influence of the stretching rate was negligible. POLYM. ENG. SCI., 55:1767–1775, 2015. © 2014 Society of Plastics Engineers     

Enhancing hydrophilicity of polyethylene terephthalate surface through melt blending

In many industrial sectors, the surface properties of polymers are of particular importance. This applies, for instance, to painting, printing, and any coating on surface of polymeric objects. Hydrophilicity and wettability characteristics are known to be determined by the chemical makeup of the polymer surface. Blending with an additive or a polymer containing high‐energy functional groups is widely recognized as a potential technique to overcome disadvantages of low surface energy of polymers due to its convenient processing. Surface migration of polyethylene glycol (PEG) in Polyethylene Terephthalate (PET) host was investigated using a low‐molecular‐weight PEG (8 kDa) because of its good hydrophilicity, low toxicity, biocompatibility, and chain mobility. A twin‐screw extruder was used to blend the materials and prepare the polymer blend films. The results of surface characterizations showed that PEG renders the PET surface more hydrophilic, but not high enough for many applications. In a second approach, the addition of a third component, polystyrene (PS), to the blend in a small amount resulted in a remarkable surface enrichment of PEG at the polymer/air interface for the ternary polymer blend (PET‐PEG‐PS). Surface analysis revealed that the surface concentration of PEG in the ternary polymer blend film was significantly larger than that of the binary one. POLYM. ENG. SCI., 55:349–358, 2015. © 2014 Society of Plastics Engineers     

Fast bit-loading algorithm for DMT systems

In this paper, a novel solution to bit-loading algorithm for Discrete MultiTone modulation (DMT) systems is proposed. Simulation results, using the carrier serving area (CSA) loops in an ADSL environment impaired by crosstalk, show that the proposed algorithm converges more rapidly than the Campello algorithm, which is the fast algorithm that can be efficiently implemented in practice among those proposed in the past.     

Limiting flux prediction during tubular ultrafiltration

Ultrafiltration of polyethylene glycol aqueous solutions was analyzed using concentration polarization-gel layer model. The model is based on coupling concentration polarization layer and gel layer growth. The concentration polarization layer development is given by the convective-diffusion equation. However, the gel layer growth model is obtained by using the experimental observations. The limiting flux was found to be proportional to the square root of the axial velocity. Beyond the critical concentration, both concentration polarization and gel formation are the main factors controlling the limiting flux in the tubular UF system. The developed semi-empirical model, which contains a single empirical constant to be evaluated from experiments, predicted satisfactorily the limiting flux data over the range of experimental variables examined in this study.     

Stabilization of Systems with Unsymmetrical Saturated Control: An LMI Approach

This paper deals with the regulator problem for linear continuous-time systems with asymmetric saturations on the control. The main contribution of this work is to extend the available results for symmetrical saturations, in term of LMIs, to systems with asymmetric saturations. Hence, LMIs formalism is obtained for the first time for asymmetrical saturation. New less conservative result on saturation is used. An example is presented to illustrate the obtained results.     

Stabilization of switching Takagi–Sugeno systems by switched Lyapunov function

This paper presents sufficient conditions for the stabilization of switching T‐S fuzzy discrete‐time linear systems. These conditions are obtained when state feedback control laws are used. The obtained results are formulated in terms of LMIs. A numerical example illustrates the technique. Copyright © 2011 John Wiley & Sons, Ltd.